[jira] [Commented] (SPARK-17971) Unix timestamp handling in Spark SQL not allowing calculations on UTC times

["Sean Owen (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/SPARK-17971?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15583018#comment-15583018 ] 

Sean Owen commented on SPARK-17971:
-----------------------------------

timestamps are not time-zone-specific (good) and any translation to calendar-related representations must be done in the context of a specific timezone. This must occur in the application code and not default to some machine's setting. You need to use methods that take a timezone. See https://spark.apache.org/docs/1.6.2/api/java/org/apache/spark/sql/functions.html#from_unixtime(org.apache.spark.sql.Column,%20java.lang.String)

> Unix timestamp handling in Spark SQL not allowing calculations on UTC times
> ---------------------------------------------------------------------------
>
>                 Key: SPARK-17971
>                 URL: https://issues.apache.org/jira/browse/SPARK-17971
>             Project: Spark
>          Issue Type: Bug
>          Components: Spark Core, SQL
>    Affects Versions: 1.6.2
>         Environment: MacOS X JDK 7
>            Reporter: Gabriele Del Prete
>
> In our Spark data pipeline we store timed events using a bigint column called 'timestamp', the values contained being Unix timestamp time points.
> Our datacenter servers Java VMs are all set up to start with timezone set to UTC, while developer's computers are all in the US Eastern timezone. 
> Given how Spark SQL datetime functions work, it's impossible to do calculations (eg. extract and compare hours, year-month-date triplets) using UTC values:
> - from_unixtime takes a bigint unix timestamp and forces it to the computer's local timezone;
> - casting the bigint column to timestamp does the same (it converts it to the local timezone)
> - from_utc_timestamp works in the same way, the only difference being that it gets a string as input instead of a bigint.
> The result of all of this is that it's impossible to extract individual fields of a UTC timestamp, since all timestamp always get converted to the local timezone.



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